Manufacturing method

Abstract

To provide a manufacturing method capable of manufacturing a molded article which achieves both strength and reduction in weight.SOLUTION: A manufacturing method includes: a shape designing step of designing a three-dimensional shape of a sand mold by a generative design; a three-dimensional molding step of molding the sand mold having the three-dimensional shape designed by the shape designing step, by a three-dimensional molding method; and a casting step of casting a molded article using the sand mold molded by the three-dimensional molding step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This disclosure relates to methods of manufacture. [Background technology]

[0002] Research and development is being conducted on techniques for creating sand molds for casting and other purposes.

[0003] In this regard, a method is known in which a sand mold used for casting is formed by a three-dimensional modeling technique that utilizes an inkjet method (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-131948 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the method described in Patent Document 1, it is difficult to optimize both the topology and the shape of the molded product in the design of the molded product to be cast. As a result, it is sometimes difficult to manufacture a molded product that is both strong and lightweight with this method. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present disclosure is a manufacturing method including a shape design process for designing a three-dimensional shape of a sand mold using generative design, a three-dimensional modeling process for modeling the sand mold in the three-dimensional shape designed in the shape design process using a three-dimensional modeling method, and a casting process for casting a molded product using the sand mold modeled in the three-dimensional modeling process. [Brief description of the drawings]

[0007] [Figure 1]1A to 1C are diagrams illustrating an example of a flow of a manufacturing method according to an embodiment. [Diagram 2] FIG. 13 is a diagram showing an example of a housing BM of a second arm of a SCARA robot manufactured by a manufacturing method X. [Diagram 3] 1 is a diagram showing an example of a housing AM of a second arm of a SCARA robot manufactured by a manufacturing method according to an embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Embodiment> Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0009] <Production method overview> First, an overview of the manufacturing method according to the embodiment will be described.

[0010] The manufacturing method according to the embodiment includes a shape design process, a three-dimensional modeling process, and a casting process. The shape design process is a process of designing a three-dimensional shape of a sand mold by generative design. The three-dimensional modeling process is a process of modeling the sand mold having the three-dimensional shape designed in the shape design process by a three-dimensional modeling method. The casting process is a process of casting a molded product using the sand mold modeled in the three-dimensional modeling process.

[0011] As a result, the manufacturing method according to the embodiment can optimize both the topology and the shape of the molded product, thereby manufacturing a molded product that is both strong and lightweight.

[0012] The manufacturing method according to the embodiment will be described in detail below.

[0013] <Manufacturing process flow> Hereinafter, the flow of the manufacturing method according to the embodiment will be described with reference to FIG.

[0014] 1 is a diagram showing an example of a flow of a manufacturing method according to an embodiment. For convenience of explanation, in the following, a person who manufactures a molded product by the manufacturing method according to an embodiment will be simply referred to as a manufacturer.

[0015] First, the manufacturer selects an object to be manufactured as a molded product (step S110). In the following, as an example, a case where the object is a housing AM of a second arm of a SCARA robot will be described. For this reason, in FIG. 1, the process of step S110 is indicated by "selection of parts." Note that the object may be an everyday item such as an accessory instead of an industrial product such as the housing AM.

[0016] Next, the manufacturer determines various constraint conditions for manufacturing the molded product (step S120). Specifically, in the process of step S120, the manufacturer determines conditions such as a weight reduction target value, an allowable displacement, an applicable material, a constraint condition, a loading condition, and a designable region as the various constraint conditions. Note that the various constraint conditions may include one or more other conditions instead of some or all of these conditions, or in addition to all of these conditions.

[0017] Next, the manufacturer derives the three-dimensional shape of the molded product by generative design based on the various constraint conditions determined in step S120 (step S130). Specifically, the manufacturer derives the three-dimensional shape of the molded product by generative design, for example, by performing the following steps in step S130. The manufacturer performs topology optimization of the shape of the molded product using the various constraint conditions and software for performing topology optimization among the software for performing generative design. After that, the manufacturer performs shape optimization of the shape of the molded product using the various constraint conditions and software for performing shape optimization among the software for performing generative design. By performing the above steps, the manufacturer derives the three-dimensional shape of the molded product by generative design in step S130. In FIG. 1, the step S130 is indicated by "shape derivation."

[0018] Next, the manufacturer adds an additional shape to the three-dimensional shape derived in step S130 (step S140). Here, the additional shape is a shape added to the three-dimensional shape, such as a shape to be a finishing allowance, a shape to be a protrusion for fixing to a jig of a cutting machine used in step S200, etc., but is not limited to these.

[0019] Next, the manufacturer designs the three-dimensional shape of the sand mold to be used for casting the molded product by determining a casting plan based on the three-dimensional shape after the additional shape has been added in step S140 (step S150).

[0020] The above-described steps S120 to S150 may be combined into one shape design step.

[0021] After the process of step S150 is performed, the manufacturer models a sand mold of the three-dimensional shape designed in step S150 by a predetermined three-dimensional modeling method (step S160). In FIG. 1, the process of step S160 is indicated by "three-dimensional modeling". This allows the manufacturer to manufacture a sand mold to be used for casting a molded product of a complex shape that cannot be split. This is a great advantage in manufacturing a sand mold to be used for casting a molded product of a shape derived by generative design, as in the process of the flowchart shown in FIG. 1. This is because many of the shapes derived by generative design are often derived as complex shapes that cannot be split. The three-dimensional modeling method used in step S160 is, for example, a modeling method using a binder jet type three-dimensional modeling device. The three-dimensional modeling device may be called a 3D (Dimension) printer. The three-dimensional modeling method used in step S160 may be a modeling method using another type of three-dimensional modeling device capable of modeling a sand mold, instead of the modeling method using a binder jet type three-dimensional modeling device. The process of step S160 may be referred to as a three-dimensional modeling process.

[0022] The manufacturer may perform additive modeling on at least a part of the sand mold formed in step S160. In this case, an additive modeling process for performing the additive modeling is added between steps S160 and S170 in the flowchart shown in Fig. 1. The additive modeling is performed by adding another sand mold to at least a part of the sand mold with an adhesive or the like. This allows the manufacturer to more reliably manufacture sand molds to be used for casting molded products with complex shapes that cannot be split.

[0023] Next, the manufacturer casts a molded product using the sand mold shaped in step S160 (step S170). The process in step S170 includes at least three processes: pouring, cooling and solidifying, and demolding. The process in step S170 may be called a casting process. The manufacturer may cast using aluminum or a magnesium alloy in step S170. This allows the manufacturer to increase the rigidity and reduce the weight of the molded product. The manufacturer may cast using other types of metals in step S170, or may cast using materials other than metals such as resin. The shape of the molded product cast in step S170 is a near-net shape. The near-net shape is a shape close to the finished product, and more specifically, a shape that can be achieved by cutting using a cutting machine such as a machining center. The manufacturer may cast a molded product using other molds such as a wooden mold together with the sand mold shaped in step S160 in step S170.

[0024] Next, the manufacturer performs heat treatment on the molded product cast in step S170 (step S180). In this way, the manufacturer adjusts the physical properties of the molded product. The heat treatment is, for example, quenching, annealing, etc., but is not limited to these. The process of step S180 may be referred to as a heat treatment process. Note that, in the flowchart shown in FIG. 1, the process of step S180 may be omitted.

[0025] Next, the manufacturer measures the three-dimensional shape of the molded product after the heat treatment in step S180 (step S190). For example, a 3D scanner, a three-dimensional measuring machine, or the like is used in the process of step S190. The process of step S190 may be referred to as a three-dimensional shape measurement process. Note that in the flowchart shown in FIG. 1, the process of step S190 may be omitted.

[0026] Next, the manufacturer cuts the molded product after the heat treatment in step S180 using a cutting machine such as a machining center based on the three-dimensional shape derived in step S130 and the three-dimensional shape measured in step S190 (step S200). The cutting by the cutting machine is, for example, but not limited to, machining with a flathead, drilling, thread cutting, etc. This allows the manufacturer to shape the molded product, which was a near-net shape, into the shape of a finished product. After the process of step S200 is performed, the manufacturer ends the process of the flowchart shown in FIG. 1. The process of step S200 may be referred to as a cutting process. Note that, in the flowchart shown in FIG. 1, the process of step S200 may be omitted.

[0027] In the manufacturing method X, which is different from the manufacturing method according to the embodiment described above, when a molded product with a complex shape that cannot be split is to be formed, the molded product is formed, for example, using a powder bed type metal 3D printer. However, the grain size of the metal powder in the metal 3D printer is about 0.05 mm. For this reason, it takes a long time to form the molded product in the metal 3D printer. This leads to low productivity and is not desirable. In addition, since the molded product formed by the metal 3D printer is formed by laminating metal powder, directionality of mechanical properties may occur. Furthermore, the molding of the molded product by the manufacturing method X has not yet been established in terms of a system for quality assurance, and the responsibility for the quality of the molded product has not been clarified. For example, the manufacturer of the metal 3D printer shows an example of parameters to be set for the metal 3D printer. However, it is known that even if the molded product is formed by the metal 3D printer using the example parameters, the quality of the molded product varies depending on other conditions. The same is true for service bureaus that purchase the metal 3D printer and make the molded products. In other words, the molding of the molded products using the metal 3D printer is a developing technology that has not yet reached the point where it can handle quality variations. Manufacturing method X is, for example, a conventional manufacturing method.

[0028] On the other hand, in the manufacturing method according to the embodiment, the molded product is formed by casting, and the sand mold used for the casting is formed by a three-dimensional modeling device using a binder jet method. Therefore, in this manufacturing method, it is possible to suppress the occurrence of directional mechanical properties in the molded product. In addition, the modeling material used in the three-dimensional modeling device is sand having a grain size of about 0.5 mm, which is 10 times the grain size of the above-mentioned metal powder, which is about 0.05 mm. That is, in this manufacturing method, compared to manufacturing method X, although it is necessary to additionally perform the molding of the sand mold, the time required for molding the sand mold can be about 10 times the time required for molding the molded product by manufacturing method X. As a result, the manufacturing method can improve productivity compared to manufacturing method X. In addition, in the casting in this manufacturing method, the molding of the sand mold can be performed in a short time compared to the molding of a conventional wooden mold. This is also one of the factors that ensure the high productivity of this manufacturing method. To summarize, this manufacturing method is a hybrid method that combines casting, a highly reliable conventional technology, with sand mold creation using generative design, an innovative technology, and can be said to be a method for creating molded products with complex shapes and high functionality.

[0029] In addition, even if it were possible to optimize the shape of a molded product in a virtual space by generative design, currently, the only method that can be selected as a method for molding a molded product with an optimized shape is additive manufacturing using a 3D printer. Therefore, it is no exaggeration to say that the manufacturing method according to the embodiment currently occupies an important position as a new method that can be selected as a method for molding a molded product with an optimized shape.

[0030] As described above, the manufacturing method according to the embodiment includes a shape design process for designing a three-dimensional shape of a sand mold by generative design, a three-dimensional modeling process for modeling a sand mold of the three-dimensional shape designed in the shape design process by a three-dimensional modeling method, and a casting process for casting a molded product using the sand mold modeled in the three-dimensional modeling process. This manufacturing method allows the manufacturing of a molded product that is both strong and lightweight.

[0031] Here, Fig. 2 is a diagram showing an example of a housing BM of a second arm of a SCARA robot manufactured by manufacturing method X. In the example shown in Fig. 2, the shape of the housing BM is an oval shape when viewed from above, and a rectangular shape when viewed from the side. The housing BM has a recess from top to bottom, and components such as a motor are mounted in the recess.

[0032] On the other hand, FIG. 3 is a diagram showing an example of the housing AM of the second arm of the SCARA robot manufactured by the manufacturing method according to the embodiment. As shown in FIG. 3, the shape of the housing AM is significantly different from the shape of the housing BM shown in FIG. 2. Specifically, in the example shown in FIG. 3, the shape of the housing AM is a space truss, and is a shape composed of multiple triangles adjacent to each other. However, the housing AM has a shape that allows parts such as a motor to be mounted. The housing AM, which is a space truss, is lighter than the housing BM when the material is the same as that of the housing BM. This is clear because the volume of the housing AM having multiple voids formed in the space truss is smaller than the volume of the housing BM. Nevertheless, the housing AM has practical strength because its shape is optimized by generative design. As a result, a SCARA robot equipped with the housing AM can realize a low inertia of the second arm, and as a result, the second arm can be operated faster. From this, it can be said that the manufacturing method is an optimal technology for manufacturing a robot arm.

[0033] The above-described contents may be combined in any manner.

[0034] <Additional Notes> [1] A manufacturing method comprising: a shape design process for designing a three-dimensional shape of a sand mold by generative design; a three-dimensional modeling process for modeling the sand mold in the three-dimensional shape designed in the shape design process by a three-dimensional modeling method; and a casting process for casting a molded product using the sand mold modeled in the three-dimensional modeling process. [2] The manufacturing method described in [1], wherein the three-dimensional modeling method is a modeling method using a binder jet type three-dimensional modeling device. [3] The manufacturing method according to [1] or [2], wherein the casting step is performed using aluminum. [4] The manufacturing method according to [1] or [2], wherein the casting step is performed using a magnesium alloy. [5] A manufacturing method described in any one of [1] to [4], further comprising an additive modeling process for additively modeling at least a portion of the sand mold formed by the three-dimensional modeling process, and the casting process for casting using the sand mold after additive modeling by the additive modeling process. [6] The manufacturing method according to any one of [1] to [5], wherein the shape of the molded product cast in the casting step is a near net shape. [7] The manufacturing method according to any one of [1] to [6], further comprising a three-dimensional shape measurement step of measuring a three-dimensional shape of the molded product cast in the casting step. [8] [7] A manufacturing method according to the present invention, comprising: a heat treatment step of performing heat treatment on the molded product cast in the casting step; and a cutting step of cutting the molded product after the heat treatment step based on the three-dimensional shape measured in the three-dimensional shape measurement step, wherein the three-dimensional shape measurement step is performed after the heat treatment step. [9] The manufacturing method described in any one of [1] to [8], wherein the molded product is a housing for a robot arm.

[0035] Although an embodiment of the present disclosure has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and may be changed, substituted, deleted, etc. without departing from the gist of this disclosure. [Explanation of symbols]

[0036] AM, BM: Housing, X: Manufacturing method

Claims

1. A shape design process to design the 3D shape of the sand mold using generative design; a three-dimensional modeling process for modeling the sand mold having the three-dimensional shape designed in the shape design process by a three-dimensional modeling method; a casting process for casting a molded product using the sand mold formed by the three-dimensional modeling process; The manufacturing method according to claim 1,

2. The three-dimensional modeling method is a modeling method using a binder jet type three-dimensional modeling device, The method of claim 1 .

3. The casting step includes casting using aluminum. The method of claim 1 .

4. The casting step includes casting using a magnesium alloy. The method of claim 1 .

5. An additive modeling process is provided for additively modeling at least a part of the sand mold modeled by the three-dimensional modeling process, The casting step performs the casting using the sand mold after additive shaping in the additive shaping step. The method of claim 1 .

6. The shape of the molded product cast by the casting process is a near net shape. The method of claim 1 .

7. A three-dimensional shape measuring step of measuring a three-dimensional shape of the molded product cast in the casting step. The method of claim 1 .

8. a heat treatment step in which heat treatment is performed on the molded product cast in the casting step; a cutting step of cutting the molded product after the heat treatment step based on the three-dimensional shape measured in the three-dimensional shape measuring step; having The three-dimensional shape measuring step is performed after the heat treatment step. The method of claim 7.

9. The molded product is a housing for a robot arm. The method of claim 1 .

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